The post-war border between Germany and Poland along the Oder-Neisse line was formally recognized by East Germany in 1950 by the Treaty of Zgorzelec, under pressure from Stalin. In 1952, recognition of the Oder–Neisse line as a permanent boundary was one of Stalin's conditions for the Soviet Union to agree to a reunification of Germany (see Stalin Note). The offer was rejected by West German Chancellor Konrad Adenauer. The official German government position on the status of former eastern territories of Germany vacated by settled German communities east of the Oder and Neisse rivers was that the areas were "temporarily under Polish [or Soviet] administration." In 1970, West Germany recognised the line as a de facto boundary in the Treaty of Warsaw.

In the Potsdam Agreement the description of the territories transferred is "The former German territories east of the Oder-Neisse line", and permutations on this description are the most commonly used to describe any former territories of Germany east of the Oder-Neisse line.

The name East Germany, a political term, used to be the common colloquial English name for the German Democratic Republic (GDR), and mirrored the common colloquial English term for the other German state of West Germany. When focusing on the period before World War II, "eastern Germany" is used to describe all the territories east of the Elbe (East Elbia), as reflected in the works of sociologist Max Weber and political theorist Carl Schmitt,[4][5][6][7][8] but because of the border changes in the 20th century, after World War II the term "east Germany" and eastern Germany in English has meant the territory of the German Democratic Republic.

In German there is only one usual term Ostdeutschland, meaning East Germany or Eastern Germany, the German rather ambiguous term never gained prevailing use for the GDR as did the English term. Since the Ostdeutschland has been used to denote the post-war and the respective five states of the reunited Germany. However, because people and institutions in the states, traditionally considered as Middle Germany, like the three southern new states Saxony-Anhalt, the Free State of Saxony and the Free State of Thuringia, still use the term Middle Germany when referring to their area and its institutions the term Ostdeutschland is still ambiguous.[9]

The Treaty of Versailles of 1919 that ended World War I restored the independence of Poland, known as the Second Polish Republic, and Germany was compelled to cede territories to it, most of which were taken by Prussia in the three Partitions of Poland, and had been part of the Kingdom of Prussia and later the German Empire for over 100 years. The territories ceded to Poland in 1919 were those with an apparent Polish majority, such as the Province of Posen, the east-southern part of Upper Silesia and the Polish Corridor.

Between the two world wars, many in Germany claimed that the territory ceded to Poland in 1919–1922 should be returned to Germany. This claim was one of the justifications for the German invasion of Poland in 1939, heralding the start of the Second World War. The Third Reich annexed the former German lands, comprising the "Polish Corridor", West Prussia, the Province of Posen, and parts of eastern Upper Silesia. The council of the Free City of Danzig voted to become a part of Germany again, although Poles and Jews were deprived of their voting rights and all non-Nazi political parties were banned. In addition to taking territories lost in 1919, Germany also took additional land that had never been German.

Two decrees by Adolf Hitler (October 8 and October 12, 1939) divided the annexed areas of Poland into administrative units:

Germany subsequently lost territories east of the Oder-Neisse Line at the end of the War in 1945, when international recognition of its right to jurisdiction over any of these territories was conditionally withdrawn. The "condition" mentioned was the Final German Peace Treaty, which was to set the actual border line, which may or may not have been the Oder-Neisse line. At Potsdam, the assumption by many was that a Final German Peace Treaty was imminent, but this turned out to be incorrect.

After World War II, as agreed at the Potsdam Conference (which met from 17 July until 2 August 1945), all of the areas east of the Oder-Neisse line, whether recognised by the international community as part of Germany until 1939 or occupied by Germany during World War II, were placed under the jurisdiction of other countries.The relevant paragraphs in the Potsdam Agreement are:[11][12][13]

The Conference examined a proposal by the Soviet Government to the effect that pending the final determination of territorial questions at the peace settlement, the section of the western frontier of the Union of Soviet Socialist Republics which is adjacent to the Baltic Sea should pass from a point on the eastern shore of the Bay of Danzig to the east, north of Braunsberg-Goldap, to the meeting point of the frontiers of Lithuania, the Polish Republic and East Prussia.
The Conference has agreed in principle to the proposal of the Soviet Government concerning the ultimate transfer to the Soviet Union of the City of Koenigsberg and the area adjacent to it as described above subject to expert examination of the actual frontier.
The President of the United States and the British Prime Minister have declared that they will support the proposal of the Conference at the forthcoming peace settlement.

VIII. Poland.

...
The British and United States Governments have taken measures to protect the interest of the Polish Provisional Government of National Unity as the recognized government of the Polish State in the property belonging to the Polish State located in their territories and under their control, whatever the form of this property may be.
...
In conformity with the agreement on Poland reached at the Crimea Conference the three Heads of Government have sought the opinion of the Polish Provisional Government of National Unity in regard to the accession of territory in the north and west which Poland should receive. The President of the National Council of Poland and members of the Polish Provisional Government of National Unity have been received at the Conference and have fully presented their views. The three Heads of Government reaffirm their opinion that the final delimitation of the western frontier of Poland should await the peace settlement.

The three Heads of Government agree that, pending the final determination of Poland's western frontier, the former German territories east of a line running from the Baltic Sea immediately west of Swinamunde, and thence along the Oder River to the confluence of the western Neisse River and along the Western Neisse to the Czechoslovak frontier, including that portion of East Prussia not placed under the administration of the Union of Soviet Socialist Republics in accordance with the understanding reached at this conference and including the area of the former free city of Danzig, shall be under the administration of the Polish State and for such purposes should not be considered as part of the Soviet zone of occupation in Germany. (Emphasis added)

The Allies also agreed that:

XII. Orderly transfer of German populations.

The Three Governments [of the Soviet Union, the United States and Great Britain], having considered the question in all its aspects, recognize that the transfer to Germany of German populations, or elements thereof, remaining in Poland, Czechoslovakia and Hungary, will have to be undertaken. They agree that any transfers that take place should be effected in an orderly and humane manner.

Expulsion is the method which, in so far as we have been able to see, will be the most satisfactory and lasting. There will be no mixture of populations to cause endless trouble. A clean sweep will be made.[14]

The problem with the status of these territories was that the Potsdam Agreement was not a legally binding treaty, but a memorandum between the USSR, the USA and the UK. It regulated the issue of the eastern German border, which was to be the Oder-Neisse line, but the final article of the memorandum said that the final decisions concerning Germany were subject to a separate peace treaty. This treaty was signed in 1990 as the Treaty on the Final Settlement with Respect to Germany.[15][16]

After the War, the so-called "German question" was an important factor of post-war German and European history and politics. The debate affected Cold War politics and diplomacy and played an important role in the negotiations leading up to the reunification of Germany in 1990. In 1990 Germany officially recognized its present eastern border at the time of its reunification in the Treaty on the Final Settlement with Respect to Germany, ending any residual claims to sovereignty that Germany may have had over any territory east of the Oder-Neisse line.

Between 1945 and 1990 the government of West Germany referred to these territories as "former German territories temporarily under Polish and Soviet administration". This terminology was used in relation to territories of eastern Germany within the 1937 Germany border, and was based on the terminology used in the Potsdam Agreement. It was used only by the Federal Republic of Germany; but the Polish and Soviet governments objected to the obvious implication that these territories should someday revert to Germany. The Polish government preferred to use the phrase "Recovered Territories", asserting a sort of continuity because parts of these territories had centuries previously been ruled by ethnic Poles.

With the rapid advance of the Red Army in the winter of 1944–1945, German authorities desperately evacuated many Germans to west of the Oder–Neisse line. The majority of the remaining German-speaking population east of the Oder–Neisse line (roughly 10 million in the ostgebiete alone) that had not already been evacuated was expelled. Although in the post-war period earlier German sources often cited the number of evacuated and expelled Germans at 16 million and the death toll at between 1.7[17] and 2.5 million,[18] today, the numbers are considered by some historians to be exaggerated and more likely in the range between 400,000 to 600,000.[19] Some present-day estimates place the numbers of German refugees at 14 million of which about half a million died during the evacuations and expulsions.[19][20]

The expansion of the European Union to Central Europe in 2004 enabled any German wishing to live and work in Poland, and thus east of the Oder-Neisse line, to do so without requiring a permit. German expellees and refugees became free to visit their former homes and set up residence, though some restrictions remained on the purchase of land and buildings.

Poland entered the Schengen Area on December 21, 2007, removing all border controls on its border with Germany.

In the course of the German reunification, Chancellor Helmut Kohl accepted the territorial changes made after World War II, creating some outrage among the Federation of Expellees, while some Poles were concerned about a possible revival of their 1939 trauma through a "second German invasion", this time with the Germans buying back their land, which was cheaply available at the time. This happened on a smaller scale than many Poles expected, and the Baltic Sea coast of Poland has become a popular German tourist destination. The so-called "homesickness-tourism" which was often perceived as quite aggressive well into the 1990s now tends to be viewed as a good-natured nostalgia tour rather than an expression of anger and desire for the return of the lost territories[citation needed].

Some organisations in Germany continue to claim the territories for Germany or property there for German citizens. The Prussian Trust (or the Prussian Claims Society), that probably has less than a hundred members,[22] re-opened the old dispute when in December 2006, it submitted 23 individual claims against the Polish government to the European Court of Human Rights asking for compensation or return of property appropriated from its members at the end of World War II. An expert report jointly commissioned by the German and Polish governments from specialists in international law have confirmed that the proposed complaints by the Prussian Trust had little hope of success. But the German government cannot prevent such requests being made and the Polish government has felt that the submissions warranted a comment by Anna Fotyga, the Polish Minister of the Foreign Affairs to "express [her] deepest concern upon receiving the information about a claim against Poland submitted by the Prussian Trust to the European Court of Human Rights".[23] On 9 October 2008 the European Court of Human Rights declared the case of Preussische Treuhand v. Poland inadmissible, because the European Convention on Human Rights does not impose any obligations on the Contracting States to return property which was transferred to them before they ratified the Convention.[24]

^The problem with the status of these territories was that in 1945 the concluding document of the Potsdam Conference was not a legally binding treaty, but a memorandum between the USSR, the USA and the UK. It regulated the issue of the eastern German border, which was to be the Oder-Neisse line, but the final article of the memorandum said that the final decisions concerning Germany were subject to a separate peace treaty. This treaty was signed in 1990 under the name of Treaty on the Final Settlement by both the German states and ratified in 1991 by the united Germany. This ended the legal limbo state which meant that for 45 years, people on both sides of the border could not be sure whether the settlement reached in 1945 might be changed at some future date.

^Each spring, millions of workmen from all parts of western Russia arrived in eastern Germany, which, in political language, is called East Elbia. fromThe Stronghold of Junkerdom, by George Sylvester Viereck. Viereck's, Volume 8. Fatherland Corporation, 1918

^Junker, Detlef; Gassert, Philipp; Mausbach, Wilfried et al., eds. (2004). The United States and Germany in the Era of the Cold War, 1945-1990: A Handbook. Publications of the German Historical Institute Volume 1 of The United States and Germany in the Era of the Cold War 2 Volume Set (illustrated ed.). Cambridge University Press. p. 105. ISBN9780521791120.|displayeditors= suggested (help)CS1 maint: Extra text (link)